Furnaces are used in a variety of industries and in a variety of ways to provide heating. For example, industrial processes in oil and gas refineries, chemical plants, or other industrial facilities often use furnaces to heat materials in order to facilitate desired chemical reactions. A furnace typically operates by receiving flows of fuel (such as fuel gas, fuel oil, coal, or wood chips) and inlet air, and the fuel is combusted in the presence of the inlet air to produce heat that is transferred to a process material. Ideally, the combustion of the fuel and the heating of the process material remain stable, and all or substantially all of the fuel entering the furnace is combusted.
Furnace flooding refers to a condition that can occur when the combustion of fuel gas in a furnace becomes unstable, such as when a ratio of the inlet air flow to the fuel gas flow moves outside of the furnace's operating envelope. When this occurs, the combustion process can become unstable or even stop, resulting in a loss of flame within the furnace. The loss of flame means that no fuel gas is being burned within the furnace. However, fuel gas may continue to be provided into the furnace, resulting in a build-up of uncombusted fuel gas in the furnace. In some circumstances, this could lead to an explosion of the furnace.